1. Field of the Invention
Embodiments of the invention relate to light source devices, analysis devices, and light source generation methods.
2. Related Art
In recent years, there have been advances in technologies relating to laser light. As a result, laser spectroscopy in which laser light absorption intensity is used to detect the amounts of specific materials in a sample has become more precise. However, there are no usable laser diodes at wavelengths from 490 nm to 630 nm. Hence as disclosed in Japanese Patent Application Laid-open No. 2008-28380 (also referred to herein as “Patent Reference 1”) and International Patent Application No. WO 2006/075760 (also referred to herein as “Patent Reference 2”), for example, techniques have been developed in which near-infrared laser light is used to obtain light in the wavelengths band of 490 nm to 630 nm, with a wavelength conversion element.
For example, Patent Reference 1 discloses a light source device in which light emitted from a laser oscillator is incident on a wavelength conversion portion and is converted into a harmonic. In this light source device, the laser oscillator has, in order, a laser light source, first fiber grating, fiber, and second fiber grating. The reflection wavelength of the second fiber grating is shifted by applying a tensile stress. The power source of the tensile stress is a pulse motor.
Patent Reference 2 discloses a light source device in which two semiconductor laser light sources, the output light wavelengths of which are different, are connected by a coupler, and the outputs made incident on a wavelength conversion module. In this light source device, the difference frequency and sum frequency of the laser light from the two semiconductor laser light sources are generated in the wavelength conversion module. By changing the magnitude of the current input to one of the semiconductor laser light sources, the wavelengths are shifted.
In general, the width of gas absorption lines is narrow. Consequently when a sample is air or another gas, and the substance for detection is a gas, in order to perform laser spectroscopy with high precision, wavelength variability is necessary enabling the sweeping of absorption lines after having made the laser line width narrower than the absorption line width. Moreover, in order to improve the precision of measurement, the laser light intensity must be modulated at high speed.
However, in the technique disclosed in Patent Reference 1, control of the laser light source output itself is necessary in order to perform intensity modulation of laser light. In this case, performing intensity modulation of laser light at high speed is difficult. And in the technique disclosed in Patent Reference 2, in order to change the wavelength of the output light, the current input to a semiconductor laser light source must be changed, and the laser light source wavelength and intensity cannot be controlled mutually independently.
Thus, as is described above, there is a need in the art for an improved light source device.